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Physical / electrical concepts
N-channel MOSFET
A transistor whose "switch" closes (conducts) when the gate is driven HIGH. Used to pull a pin DOWN to GND in both I²C and the bottom half of an SPI output.
How it looks
Drawing
N-CHANNEL: SWITCHES THINGS TO GROUND
gate
drain
source
Source to ground; a HIGH gate turns it on.
How it works
N-CHANNEL MOSFET PULLING A LINE LOW
line (with a pull-up)
ground
gate LOW
off: the line stays high
gate HIGH
on: the line is pulled to ground
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Where it fits
Its mirror is the
p-channel MOSFET
; terminals:
drain, source and gate
. A classic part is the
BSS138
.
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